Detecting conduction timing

ABSTRACT

An example method includes analyzing morphology and/or amplitude of each of a plurality of electrophysiological signals across a surface of a patient&#39;s body to identify candidate segments of each signal satisfying predetermined conduction pattern criteria. The method also includes determining a conduction timing parameter for each candidate segment in each of the electrophysiological signals.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional patentapplication No. 62/331,116 filed on May 3, 2016, and entitled DETECTINGCONDUCTION TIMING, which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

This disclosure relates to detecting conduction timing and correspondingpatterns thereof.

BACKGROUND

Existing approaches to extract the activation temporal information fromelectrograms may involve (1) aggressively filtering the virtualelectrogram to remove noise, and (2) identifying the zero-crossings offiltered signals at the downward slopes as the local activation time.The disadvantage of this existing approach is that the aggressivefiltering, while removing noise, may also filter out part of the signal,and therefore leading to loss of information and distortion of thedownward slopes in the electrogram. In addition, the zero-crossing ofelectrograms, which serves as a surrogate of the activation time, maynot be a robust measure in the presence of noise (e.g., baselinedrifting) during the body-surface recordings.

SUMMARY

This disclosure relates to detecting conduction timing.

As one example, a method includes analyzing morphology and/or amplitudeof each of a plurality of electrophysiological signals across a surfaceof a patient's body to identify candidate segments of each signalsatisfying predetermined conduction pattern criteria. The method alsoincludes determining a conduction timing parameter for each candidatesegment in each of the electrophysiological signals. In some examples,one or more non-transitory computer-readable media stores instructionsis programmed to perform the method.

As another example, a system includes memory to store machine readableinstructions and data. The data includes electrical data representingelectrophysiological signals distributed across a body surface. One ormore processors access the memory and execute the instructions. Theinstructions include a conduction pattern estimator that analyzesmorphology and/or amplitude of each of a plurality ofelectrophysiological signals across a surface of a patient's body toidentify candidate segments of each of the plurality of signals thatsatisfy predetermined conduction pattern criteria. A conduction patternparameter identifier determines a conduction timing parameter for eachof the identified candidate segments in the electrophysiologicalsignals. An output engine provides output data to drive a display with agraphical map that includes a visualization of or derived from theconduction timing parameters determined for the electrophysiologicalsignals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example of a system to estimate conduction of patternsfrom electrophysiological data.

FIG. 2 depicts an example of a dynamic activation time estimator thatcan utilize conduction pattern estimation from FIG. 1.

FIG. 3 depicts an example of a reconstructed electroanatomic signal.

FIG. 4 depicts another electrogram signal demonstrating detection ofactivation time for a segment of such signal.

FIG. 5 is a flow diagram illustrating a method for detecting conductionpatterns.

FIG. 6 depicts graphical maps demonstrating wave fronts duringarrhythmogenic driver activity.

FIGS. 7 and 8 demonstrate examples of graphical maps that can begenerated.

FIG. 9 depicts an example of a system to perform diagnostics and/ortreatment with respect to a patient.

DETAILED DESCRIPTION

This disclosure relates to detecting conduction timing, such asactivation time and corresponding conduction patterns or sequences inelectrical signals distributed across a surface (e.g., an exterior orinterior surface of) a patient's body. This disclosure also provides avisualization (e.g., a graphical user interface (GUI)) based on detectedconduction patterns that can be utilized to provide an interactivegraphical map.

As one example, systems and methods are provided to detect a conductiontiming from electrophysiological signals, such as can be stored inmemory as electrical data representing electrograms that have beenreconstructed for a cardiac envelope (e.g., epicardial surface oranother cardiac surface) or another surface of the patient's body (e.g.,an external body surface).

As an example, the detection can include analyzing morphology and/oramplitude of each of a plurality of electrophysiological signals todetermine candidate segments of each signal satisfying predeterminedconduction pattern criteria (e.g., slope and amplitude criteria). Theelectrophysiological signals may include a set of electrogramdistributed across a surface of a patient's body. Another portion ofdownward sloping segments of each of the signals that do not satisfy allthe predetermined conduction pattern criteria can be designated aspotential (or questionable) segments for further evaluation. Suchfurther evaluation of the potential segments can include determining ifeach of the potential segments of the electrophysiological signals isspatially and temporally consistent with neighboring segments that hadalready been selected as one of the candidate segments. A respectivesegment that has been designated as a potential segment can be removedfrom further consideration if it is determined that it is not spatiallyand/or temporally consistent with neighboring candidates. Such spatialand temporal consistency across the surface can indicate the presence ofa conduction pattern, thereby verifying whether or not a potentialsegment contains an activation time that is spatially and temporallylinked with an identifiable conduction pattern. The candidate segmentsfor each of the plurality of signals can be aggregated together and aconduction pattern parameter be identified for each candidate segment,such as corresponding to a consistently selected point along the segment(e.g., a fixed percentage of the peak-to-valley segment amplitude). Theconduction pattern parameter can include activation time for eachcandidate sequence, which can be combined to determine a sequence ofactivation times across the cardiac envelope.

The approach herein is particularly robust for analysis of electricalactivity that occurs during abnormal rhythms (arrhythmogenic activity).For example, non-invasive mapping may be employed to computereconstructed electrograms on the cardiac envelope (e.g., the outersurface of the heart) from body-surface electrical measurements. Eachelectrogram contains the information of activation and repolarization ateach location of the cardiac envelope (atria or ventricle). On the otherhand, manually reviewing the electrograms does not easily reveal aconduction pattern. This is especially true when reviewing thearrhythmia data, where the conduction is complex but the understandingof the complex conduction is urgently needed.

This disclosure thus facilitates identifying the conduction patternsfrom electrograms. The conduction pattern revealed during abnormalrhythms can then enable diagnosis and treatment of the electricaldysfunction of the heart. The conduction pattern can be detected whileavoiding signal distortion due to aggressive filtering, as well as doesnot require any phase calculation. Thus, the approach herein is thuscapable of analyzing electrograms with shorter duration. As a result,systems and methods disclosed herein can further enhance the accuracy ofour non-invasive mapping, which would lead to better clinical outcomes.

As a further example, this disclosure includes an interactive graphicaluser interface (GUI) that provides a visualization scheme forarrhythmogenic drivers that highlights arrhythmogenic activity (e.g.,rotations and/or focal points) in a color map. The GUI further enables auser to select a driver, and review and ignore individual contributingdrivers within a single map, for example. The GUI implements a filteringmechanism on the driver map that allows the user to view un-reviewed,final, or all drivers, for example.

FIG. 1 depicts an example of a system 10 that can be utilized todetermine conduction patterns as well as to generate graphical maps 38that can be visualized on a display 12. The system 10 includes memory14, which can include one or more non-transitory machine-readable mediathat stores instructions and data. The system 10 also includes aprocessor 16, which can include one or more processing cores, to accessthe memory and execute corresponding instructions demonstrated withinthe processor block 16.

In the example of FIG. 1, the memory stores electrophysiological data18. The electrophysiological data can correspond to unipolarelectrograms or other electrophysiological signals that can be measuredor estimated based upon measured or electrical activity across thesurface of a patient's body. For example, the electrophysiological data18 can correspond to electroanatomical data that has been reconstructedonto a cardiac envelope of the patient's heart by solving the inverseproblem with respect to electrical signals measured non-invasivelyacross a surface of a patient's body, such as the patient's thorax or aportion thereof. Examples of sensors that may be utilized to acquire thebody surface electrical activity are disclosed in U.S. Pat. No.9,549,683 and International application No. PCT/US20091063803.

These and other various measurement systems can be utilized to acquirethe body surface electrical measurements non-invasively that can beutilized to provide the electrophysiological data 18 that can eithercorrespond to live data that is acquired intraprocedurally, or theelectrophysiological data 18 can correspond to data that has beenacquired a priori and stored in the memory 14, such as part of aprevious electrophysiology (EP) study or acquired during anotherintervention. Each of the signals in the electrophysiological data 18represent the electrical signals at nodes spatially distributed across asurface (e.g., body surface or cardiac surface envelope), and thus mayinclude waveform information and geometry information for the nodes intwo- or three-dimensional space.

The processor 16 executes machine readable instructions that include aconduction pattern estimator 20. The conduction pattern estimator 20 isprogrammed to identify the conduction pattern parameter (e.g.,corresponding to an activation time) for selected segments of each ofthe electrophysiological signals represented by the data 18. Asmentioned, electrophysiological data 18 can correspond to a plurality ofpoints distributed across a surface, such as an anatomical surface or anenvelope having a known geometry with respect to an anatomicalstructure.

In the example of FIG. 1, the conduction pattern estimator 20 includes asignal segment detector 22. The signal segment detector 22 is used todetect segments of signal waveforms having a morphology known to beconsistent with the conduction timing parameter of interest. In someexamples, the pattern estimator 20 suggests a set of potential segmentsand the user selects a portion of suggested segments for evaluation inresponse to a user input via GUI. Thus the user can either continue withevaluating the selected portion of the segments for calculatingconduction timing and other parameters or provide a user input todiscard them, such as by tagging the data with information to enablesuch data to be ignored.

For sake of consistency and ease of explanation, the conduction timingparameter of interest is disclosed herein mainly as an activation timeparameter. In other examples, the conduction timing parameter mayrepresent other temporal parameters that occur repeatedly over time inan electrophysiological signal of interest over time, such as providingan indication of a repolarization time or a relative activation andrepolarization time.

As one example, the signal segment detector 22 includes a slopecalculator 23 and a peak detector 25. The slope calculator 23 computesthe slope of segments of each the signal waveforms. The peak detector 25identifies points along the signal waveforms corresponding to peaks,which include positive peaks as well as negative peaks (troughs). Forinstance, the peak detector 25 identifies peaks as points that changefrom positive slope to negative slope or from negative slope to positiveslope, such as determined as the time-based derivative of the computedslope. The signal segment detector 22 utilizes the computed slope andpeaks to identify signal segments having a downward slope that ispotentially associated with an activation (referred to as “downwardsloping segments”). Each downward sloping segment thus can be defined bya portion of a given signal waveform determined to have a negative slopeand extends between a detected peak and trough of the given signal. Thedownward sloping segment may be substantially linear or non-linear(curved).

A signal segment analyzer 24 analyzes each of the detected signalsegments (e.g., downward sloping segments detected by detector 22) toidentify segments that the system 10 is to consider as true activations.For example, the signal segment analyzer 24 can include a morphologyanalysis component 26 and an amplitude analysis component 28. The signalsegment analyzer 24 thus can select a portion of the candidate segmentsfrom the detected signal segments based on the morphology and amplitudecomponents 26 and 28 ascertaining that the amplitude and duration of thesignals satisfy certain criteria (e.g., a sufficiently large amplitudeand sufficiently short duration). The downward sloping segmentssatisfying such morphology and amplitude criteria can be stored inmemory 14 as candidate data representing a set of candidate segments.

The signal segment analyzer 24 can employ a spatial analysis component30 to evaluate the remaining set of the detected signal segments thatdid not satisfy the morphology and amplitude criteria applied bycomponents 26 and 28. The set of remaining signal segments may bereferred to as potential candidate segments. For instance, the spatialanalysis component 30 can analyze each of the questionable signalsegments relative to one or more neighboring candidate segments at nodeslocated near (e.g., within a predetermined distance from) the nodelocation for each respective questionable signal segment and within atime window of the time interval that defines the segment. The timewindow may be fixed or vary as a function the distance between the nodesbeing evaluated. The spatial analysis component 30 thus can determine ifeach questionable signal segment has one or more neighbor nodes thathave been determined (e.g., by morphology and amplitude components 26,28) to exhibit activation at a sufficiently high level of confidencewithin a time window of the respective questionable segment. That is, ifa given signal segment exhibits activation at a particular location onthe surface, there should be one or more neighboring signal segmentsexhibiting activation that are spatially and temporally consistent withthe given signal segment. Consequently, candidate signal segments thathave been determined to exhibit an activation (e.g., based uponmorphology and amplitude components 26 and 28) can be used by the signalsegment analyzer 24 to confirm whether or not questionable signalsegments at neighboring should be discarded as noise or be considered asincluding a true activation time.

By way of example, if no neighboring signal segments have beendetermined to exhibit activation time, then the questionable signalsegments can be discarded. If neighboring signal segments exhibit anactivation time within a time window of a given questionable signalsegments, there is an increased likelihood that the given questionablesignal segment likewise exhibits an activation time and thus can bedesignated (by the spatial analysis component 30) as another candidatesegment. The set of candidate segments determined by the spatialanalysis component 30 and the set of candidate segments determined bythe morphology and amplitude components 26 and 28 can be aggregatedtogether to provide an aggregate set of candidate segments that exhibitactivation time. The aggregate set of candidate segments can be storedin memory 14.

The conduction pattern estimator 20 also includes a conduction patternparameter identifier 32 to determine a conduction parameter for eachcandidate segment that has been identified. As disclosed herein, theconduction pattern parameter identifier 32 can calculate the activationtime as a point in time within the time interval for each of thecandidate signal segments. For example, the identifier 32 can determinethe activation time as any point around the downward sloping segmentthat is consistently selected from each downward sloping candidatesignal segment. As one example, the identifier 32 can designate theactivation time as the point in time when the signal reaches one-half ofthe amplitude between the peak and trough in the downward sloping signalsegment (i.e., 50% of the downward slope). Of course any percentage ofthe amplitude could be used.

In some examples depending upon noise or signal morphology, as disclosedherein with respect to FIG. 2, the conduction pattern parameteridentifier 32 can compute the activation time according to one or moredifferent approaches. For instance, the conduction pattern identifier 32can be programmed to calculate the maximum derivative of the negativeslope of the candidate segment or, in other examples, as the zerocrossing point of the negative sloping candidate segment. The activationtime that is determined by the pattern identifier 32 for each candidatesignal segment can be stored in memory 14, such as corresponding to atime indexed indication with respect to each of the plurality of signalsrepresented by the data 18.

As a further example, the processor 16 can include instructionscorresponding to an arrhythmogenic activity calculator 34. Thearrhythmogenic activity calculator 34 can be programmed to characterizethe electrophysiological data 18 across the surface. Some specificexamples of the types and forms arrhythmogenic drivers that thearrhythmogenic activity calculator 34 can compute include rotations,trajectories of rotations, wave front lines, focal sources and focalsustainability. Further examples on computing such arrhythmogenicdrivers are disclosed in U.S. Pat. Pub. 2014/0336520, corresponding toU.S. application Ser. No. 14/273,458, filed May 8, 2014, and entitledANALYSIS AND DETECTION FOR ARYTHMIA DRIVERS, which is incorporatedherein by reference. Further examples of other types of calculationsthat can be computed by the arrhythmogenic activity calculator 34 andprovide related visualizations to the display 12 are disclosed inInternational Publication No. WO2014/113555, filed Jan. 16, 2014, andentitled FOCAL POINT IDENTIFICATION AND MAPPING, and in InternationalPublication No. WO2014/113672, filed Jan. 17, 2014, and entitled WAVEFRONT DETECTION FOR ELECTROPHYSIOLOGICAL SIGNALS, each of whichpublications is incorporated herein by reference.

An output engine 36 can be utilized to generate one or more graphicalmaps 38 that can be presented on the display 12. For example, the outputengine can generate an activation map based on the activation timesdetermined by the conduction pattern estimator 20. This can be for aselected set of the signals distributed across the surface or for theentire surface and for one or more time intervals of interest, which canbe selected in response to a user input. Examples of the types of outputvisualizations and maps that can be generated are disclosed herein (see,e.g., FIGS. 6, 7 and 8) as well as those disclosed in theabove-incorporated U.S. Pat. Pub. 2014/0336520, InternationalPublication No. WO2014/113672 and/or International Publication No.WO2014/113672.

As disclosed herein, in some examples, the electrophysiological data 18is spatially and temporally consistent across the entire cardiac surfacesuch that a conduction pattern (activation) map can be generated for theentire cardiac surface over one or more time intervals. Similarly, thearrhythmogenic activity that is determined by the calculator 34 can alsobe temporally and spatially consistent such that the resulting graphicalmap of the cardiac activity can be superimposed on a graphicalrepresentation of a portion or the entire heart. The output engine 36can also include a user interface that can be utilized to set parametersfor the graphical map and to otherwise interact with and select portionsof the electrophysiological data 18 in response to user input, such asdisclosed herein.

FIG. 2 depicts an example of a dynamic activation time estimator 50 suchas can utilize the conduction pattern estimator 20. For example, thedynamic activation time estimator 50 can include a plurality ofinstances of activation time calculators 52 through 54 demonstrated atActivation Time Calc_1 through Activation Time Calc_N, where N positiveinteger greater than or equal to 2. The estimator 50 thus can employ anyactivation time calculator 52 through 54 to compute activation time forthe plurality of signals demonstrated as reconstructed electroanatomicdata 56. Each of the activation time calculators 52 through 54 canimplement a different calculation function for computing activationtimes. For example, one of the calculators is configured as theconduction pattern estimator 20 of FIG. 1, another of the calculatorscan implement a zero crossing detector and still another calculatorcomputes a maximum derivative of the negative slope to determineactivation time. Those skilled in the art thus will appreciate variousfunctions that can be utilized to determine activation time for thesignals represented by the electroanatomic data 56.

For example, reconstructed electroanatomic data 56 can be stored inmemory and include both geometry data 57 and electrical data 59 for acardiac envelope for which the signals have been reconstructed bysolving the inverse problem based upon non-invasively measuredelectrical signals. Thus, for each of the plurality of signalsdistributed across the cardiac envelope for one or more time intervals,the estimator 50 can employ a selected one of the activation timecalculators 52 through 54 for computing the activation time for each ofthe respective segments. A common activation time calculator can be usedfor each of the signals or different activation time calculators can beused to compute the activation time for different segments of the samesignal location for different time segments.

The estimator 50 includes a selector 58 to select which of theactivation time calculators 52 through 54 to utilize for computing theactivation times for each given segment. For example, the selector 58can include a noise analysis component 60 and a morphology analysiscomponent 62, which can be programmed to analyze noise and morphology,respectively, of each of the signals. If the selector 58 otherwiseascertains that the signal exhibits a significant amount of noise (e.g.,greater than a predetermined noise threshold), the selector 58 canselectively apply an activation time calculator 52 to filter the signaland apply a zero crossing detector or a maximum derivative of thenegative slope for the potential candidate segment to determine theactivation time. If the selector 58, based upon the noise analysiscomponent 60 and/or the morphology analysis component 62, determinesthat the downward sloping segment has a sufficiently large amplitude(e.g., greater than an amplitude threshold) and a sufficient duration(e.g., having a duration that extends at least a minimum duration), theselector 58 can select a different activation time calculator 54. Forexample, where the selector components 60 and 62 determine that thedownward sloping segment has a sufficient signal-to-noise ratio andexceeds a minimum threshold duration, the selector 58 can select one ofthe activation time calculators 52-54 corresponding to the conductionpattern estimator 20 disclosed with respect to FIG. 1. The estimator 50can in turn generate an activation time data 66 that is stored in memoryand be associated with the reconstructed electroanatomic data by beingindexed with respect time.

FIG. 3 depicts an example of a signal 70 demonstrating a downwardsloping portion that has been detected (by signal segment detector 22).Also shown in FIG. 3 is an activation time identified at 72 (identifiedby conduction pattern parameter identifier 32).

FIG. 4 demonstrates another signal 76 in which a selected portion of thesignal demonstrated within a dotted box 78 is enlarged. The enlargedportion of the signal demonstrates an example where the activation timeis determined at the 50% of the downward sloping segment, indicated at80. This is at one-half of the amplitude between the peak and the trough82 of the signal. Also demonstrated in the example of FIG. 4, a portionof the signal segment before and after the identified activation timecan be selected to visualize a pre-activation time window for 80% to 50%of the segment as well as a post-activation time window from 50% to 20%of the amplitude relative to the identified activation time at 80. Thesepre and post-activation time windows thus can be visualized on agraphical map as regions extending along opposing sides of theactivation wave front pattern, such as shown in FIG. 6.

FIG. 5 is a flow diagram demonstrating an example method 90 to determineconduction patterns and conduction pattern parameters (activation times)for a plurality of electrophysiological signals (e.g., reconstructedelectrograms). The method further can be implemented generate acorresponding output for visualization of one or more electricalcharacteristics of a patient's heart, including the conduction patternsand associated conduction pattern parameters. The method 90 begins at 92in which electrograms (e.g., data 18, 56) are stored. The electrograms,for example, correspond to unipolar electrograms that have beenreconstructed (e.g., by electrogram reconstruction 182) onto a cardiacenvelope with respect to a patient's heart surface based on signalsmeasured (e.g., by sensors 164) non-invasively across a patient's body,such as disclosed herein. At 94, signals are analyzed (e.g., by analyzer24) to identify candidate signal segments. For example, morphology andamplitude of the signals can be analyzed to identify the candidatesegments.

Candidate segments satisfying amplitude and duration criteria can beidentified at 96. For example the candidates identified at 96 can definea set of downward sloping segments having a sufficiently large amplitude(e.g., exceeding an amplitude threshold) and short duration (e.g., lessthan a predetermined time interval) so that they can be consideredconfidently as exhibiting to conduction pattern activities, such asactivation. At 98, downward sloping segments not meeting therequirements of large amplitude and short duration (per analysis at 96)or otherwise exhibiting significant amounts of noise can be identified(e.g., by analyzer 24) as potential segments. The method 90 thus firstfinds all the downward slopes that can be potentially associated withactivation, and then puts all these downward slopes into two categories:one group of downward slopes that are associated with sufficiently largeamplitude and short durations (based on applying amplitude andmorphology criteria) and are considered as exhibiting true activationactivity; and the other group, where the amplitude is small or containnoise, is defined as questionable slopes that could either due todamaged (but still functional) heart tissue or due to noise or far-fieldsensing.

The potential segments identified at 98 thus may define a set ofquestionable downward sloping segments requiring further analysis (e.g.,by analyzer 24) at 100. For example, at 100, a determination is madewhether each potential segment is spatially and temporally consistentwith confident neighboring segments, namely those candidate segmentsidentified at 96. That is, around a true activation at a particularlocation on the surface, there should be a neighboring activationhappening at the same or similar time. In contrast, noise-associatedslopes (due to its stochastic nature) are spatially isolated andtherefore have low chance to have spatial continuity. If thedetermination at 100, by checking the neighborhood activation of forpotential signal segments exhibiting questionable morphology, ascertainspotential segments that do not have sufficient spatial continuity withneighboring nodes, the method proceeds to 108. Thus, at 108, potentialsegments can be discarded due to exhibiting noise or otherwise lackingsufficient continuity with neighboring candidate segments. If apotential segment from 98 is spatially and temporally consistent withneighboring identified candidate segments (those considered as trueactivations at 96), the method can proceed to 102. At 102, the set ofcandidate segments identified at 96 can be combined with the set ofsegments identified at 100 as being spatially and temporally consistentwith its neighboring segments.

At 104, a conduction pattern parameter (e.g., surrogate activation timeparameter) can be identified (e.g., by conduction pattern identifier 32)for each candidate segment in the combined set of candidate segments.For example, the conduction pattern parameter provides a surrogateactivation time, such as 50% of the amplitude of the downward slopingsegment, such as disclosed herein or another location that can beconsistently applied to the downward sloping segments. At 106, an outputcan be generated to display. For example, the output can include asequence of activation snapshots in which the activation time can bedisplayed for different time indices, such as the graphical maps 120shown in FIG. 6.

In the example of FIG. 6, the activation time can be demonstrated as awave front or line pattern 122, 124, 126, 128, 130, 132 corresponding toactivation times determined (e.g., by the method 90) for each of theplurality of points across the surface of a cardiac envelope (heartmodel) for each of a plurality of different time frames. Additionally,pre- and post-activation regions with respect to the activation time canfurther be visualized on the surface of the heart model according to adefined color scale, thereby bordering the identified activation timewave front on the surface. In other examples, the determined activationtime may be shown in a single dynamic graphical map showing propagationof the wave front and associated pre and post regions across the heartmodel over at time interval.

FIG. 7 depicts an example of a graphical map 134 of a heart in which aplurality of arrhythmogenic drivers are visualized on the heart by acorresponding color scale also superimposed on the heart map. In FIG. 7,the map includes an indication of the number of focal points that occurat corresponding focal regions across the surface of the heart model134. A similar map can be generated based upon the number of focalpoints on the surface of the heart for any number of time stamps and canbe displayed in a sequence (e.g., as a series of frames) to demonstratethe movement of focal points and changes.

FIG. 8 depicts an example of another graphical map 140 of the heartdemonstrating the number of rotational activities distributed across thesurface. On the three-dimensional heart model also demonstrated aretrajectory of rotors 142 across the surface over a selected timeinterval. The number of rotational activities for different regionsacross a heart are also indicated numerically in the graphical map thatis generated.

In each of FIGS. 7 and 8, the GUI can be activated in response to a userinput to document user review of each indication of the arrhythmogenicactivity (e.g., rotational and/or focal activity) displayed in thegraphical map 134, 140 or the GUI somewhere else, more generally. Forinstance, in response to a corresponding user input interacting with thedisplayed indication of arrhythmogenic activity (e.g., on the map ofheart surface or an adjacent list) data can be stored in memory todocument user review of each indication of the arrhythmogenic activity.In this way, user review can be facilitated as rotational activities andfocal activities can be marked as reviewed or not reviewed.Additionally, the GUI can enable a user to remove a given indication ofthe arrhythmogenic activity displayed in the graphical map in responseto a user input. For example, a user can employ a user input device(e.g., mouse or touch screen interface) to reject one or more rotationalactivities or focal activities that are displayed on the map. The act ofremoval further can be tracked to document each instance of the userreview and removal. Notes can also be provided and stored in memory ifthe user decides to document reasons for a decision to remove or retainthe displayed indication of arrhythmogenic activity.

FIG. 9 depicts an example of a system 150 that can be utilized forperforming diagnostics and/or treatment of a patient. In some examples,the system 150 can be implemented to generate corresponding maps for apatient's heart 152 in real time as part of a diagnostic procedure(e.g., an electrophysiology study) to help assess the electricalactivity and identify arrhythmia drivers for the patient's heart.Additionally or alternatively, the system 150 can be utilized as part ofa treatment procedure, such as to help a physician determine parametersfor delivering a therapy to the patient (e.g., delivery location, amountand type of therapy) based on one or more identified arrhythmia drivers.For example, a catheter, such as a pacing or an ablation catheter,having one or more therapy delivery devices 156 affixed thereto can beinserted into a patient's body 154 as to contact the patient's heart152, endocardially or epicardially. The placement of the therapydelivery device 156 can be guided according to the location of one ormore arrhythmia drivers (e.g., stable rotational activity, foci,fast-firing locations or the like) that have been identified asdisclosed herein. The guidance can be automated, semi-automated or bemanually implemented based on information provided. Those skilled in theart will understand and appreciate various type and configurations oftherapy delivery devices 156 that can be utilized, which can varydepending on the type of treatment and the procedure. For instance, thetherapy device 156 can be configured to deliver electrical therapy,chemical therapy, sound wave therapy, thermal therapy or any combinationthereof.

By way of example, the therapy delivery device 156 can include one ormore electrodes located at a tip of an ablation catheter configured togenerate heat for ablating tissue in response to electrical signals(e.g., radiofrequency energy) supplied by a therapy system 158. In otherexamples, the therapy delivery device 156 can be configured to delivercooling to perform ablation (e.g., cryogenic ablation), to deliverchemicals (e.g., drugs), ultrasound ablation, high-frequency ablation,or a combination of these or other therapy mechanisms. In still otherexamples, the therapy delivery device 156 can include one or moreelectrodes located at a tip of a pacing catheter to deliver electricalstimulation, such as for pacing the heart, in response to electricalsignals (e.g., pacing pulses) supplied by a therapy system 158. Othertypes of therapy can also be delivered via the therapy system 158 andthe invasive therapy delivery device 156 that is positioned within thebody.

As a further example, the therapy system 158 can be located external tothe patient's body 154 and be configured to control therapy that isbeing delivered by the device 156. For instance, the therapy system 158includes controls (e.g., hardware and/or software) 160 that cancommunicate (e.g., supply) electrical signals via a conductive linkelectrically connected between the delivery device (e.g., one or moreelectrodes) 156 and the therapy system 158. The control system 160 cancontrol parameters of the signals supplied to the device 156 (e.g.,current, voltage, repetition rate, trigger delay, sensing triggeramplitude) for delivering therapy (e.g., ablation or stimulation) viathe electrode(s) 154 to one or more location of the heart 152. Thecontrol circuitry 160 can set the therapy parameters and applystimulation based on automatic, manual (e.g., user input) or acombination of automatic and manual (e.g., semiautomatic) controls. Oneor more sensors (not shown) can also communicate sensor information backto the therapy system 158. The position of the device 156 relative tothe heart 152 can be determined and tracked intraoperatively via animaging modality (e.g., fluoroscopy, x-ray), a mapping system 162,direct vision or the like. The location of the device 156 and thetherapy parameters thus can be combined to determine correspondingtherapy parameter data.

Before, during and/or after delivering a therapy via the therapy system158, another system or subsystem can be utilized to acquireelectrophysiology information for the patient. In the example of FIG. 4,a sensor array 164 includes one or more electrodes that can be utilizedfor recording patient electrical activity. As one example, the sensorarray 164 can correspond to a high-density arrangement of body surfacesensors (e.g., greater than approximately 200 electrodes) that aredistributed over a portion of the patient's torso for measuringelectrical activity associated with the patient's heart (e.g., as partof an electrocardiographic mapping procedure). An example of anon-invasive sensor array that can be used is shown and described inInternational application No. PCT/US2009/063803, filed 10 Nov. 2009,which is incorporated herein by reference. Other arrangements andnumbers of sensing electrodes can be used as the sensor array 164. As anexample, the array can be a reduced set of electrodes, which does notcover the patient's entire torso and is designed for measuringelectrical activity for a particular purpose (e.g., an array ofelectrodes specially designed for analyzing AF and/or VF) and/or formonitoring a predetermined spatial region of the heart.

One or more sensors may also be located on the device 156 that isinserted into the patient's body. Such sensors can be utilizedseparately or in conjunction with the non-invasive sensors 164 formapping electrical activity for an endocardial surface, such as the wallof a heart chamber, as well as for an epicardial surface. Additionally,such electrode can also be utilized to help localize the device 156within the heart 152, which can be registered into an image or map thatis generated by the system 150. Alternatively, such localization can beimplemented in the absence of emitting a signal from an electrode withinor on the heart 152.

In each of such example approaches for acquiring patient electricalinformation, including invasively, non-invasively, or a combination ofinvasive and non-invasive sensing, the sensor array(s) 164 provide thesensed electrical information to a corresponding measurement system 166.The measurement system 166 can include appropriate controls and signalprocessing circuitry 168 for providing corresponding measurement data170 that describes electrical activity detected by the sensors in thesensor array 164. The measurement data 170 can include analog and/ordigital information (e.g., corresponding to electrical data 59).

The control 168 can also be configured to control the data acquisitionprocess (e.g., sample rate, line filtering) for measuring electricalactivity and providing the measurement data 170. In some examples, thecontrol 168 can control acquisition of measurement data 170 separatelyfrom the therapy system operation, such as in response to a user input.In other examples, the measurement data 170 can be acquired concurrentlywith and in synchronization with delivering therapy by the therapysystem, such as to detect electrical activity of the heart 152 thatoccurs in response to applying a given therapy (e.g., according totherapy parameters). For instance, appropriate time stamps can beutilized for indexing the temporal relationship between the respectivemeasurement data 170 and therapy parameters use to deliver therapy as tofacilitate the evaluation and analysis thereof.

Since the measurement system 166 can measure electrical activity of apredetermined region or the entire heart concurrently (e.g., where thesensor array 164 covers the entire thorax of the patient's body 154),the resulting output data (e.g., visualizing attributes of identifiedconduction patterns, such as rotational activity and/or otherelectrocardiographic maps) thus can also represent concurrent data forthe predetermined region or the entire heart in a temporally andspatially consistent manner. The time interval for which the outputdata/maps are computed can be selected based on user input (e.g.,selecting a timer interval from one or more waveforms). Additionally oralternatively, the selected intervals can be synchronized with theapplication of therapy by the therapy system 158.

For the example where the electrical measurement data is obtainednon-invasively (e.g., via body surface sensor array 164), electrogramreconstruction 180 can be programmed to compute an inverse solution andprovide corresponding reconstructed electrograms based on the processsignals and the geometry data 172. The reconstructed electrograms thuscan correspond to electrocardiographic activity across a cardiacenvelope, and can include static (three-dimensional at a given instantin time) and/or be dynamic (e.g., four-dimensional map that varies overone or more time intervals). Examples of inverse algorithms that can beutilized in the system 10 include those disclosed in U.S. Pat. Nos.7,983,743 and 6,772,004, which are incorporated herein by reference. TheEGM reconstruction 180 thus can reconstruct the body surface electricalactivity measured via the sensor array 164 onto a multitude of locationson a cardiac envelope (e.g., greater than 1000 locations, such as about2000 locations or more). In some examples, the mapping system 162 cancompute electrical activity over a sub-region of the heart based onelectrical activity measured invasively, such as via a basket catheteror other form of measurement probe.

As disclosed herein, the cardiac envelope can correspond to a threedimensional surface geometry corresponding to a patient's heart, whichsurface can be epicardial or endocardial. Alternatively or additionally,the cardiac envelope can correspond to a geometric surface that residesbetween the epicardial surface of a patient's heart and the surface ofthe patient's body where the sensor array 164 has been positioned.Additionally, the geometry data 172 that is utilized by the electrogramreconstruction 180 can correspond to actual patient anatomical geometry,a preprogrammed generic model or a combination thereof (e.g., a modelthat is modified based on patient anatomy).

As an example, the geometry data 172 may be in the form of graphicalrepresentation of the patient's torso, such as image data acquired forthe patient. Such image processing can include extraction andsegmentation of anatomical features, including one or more organs andother structures, from a digital image set. Additionally, a location foreach of the electrodes in the sensor array 164 can be included in thepatient geometry data 172, such as by acquiring the image while theelectrodes are disposed on the patient and identifying the electrodelocations in a coordinate system through appropriate extraction andsegmentation. Other non-imaging based techniques can also be utilized toobtain the position of the electrodes in the sensor array, such as adigitizer or manual measurements.

As mentioned above, the geometry data 172 can correspond to amathematical model, such as can be a generic model or a model that hasbeen constructed based on image data for the patient. Appropriateanatomical or other landmarks, including locations for the electrodes inthe sensor array 164 can be identified in the geometry data 172 tofacilitate registration of the electrical measurement data 170 andperforming the inverse method thereon. The identification of suchlandmarks can be done manually (e.g., by a person via image editingsoftware) or automatically (e.g., via image processing techniques).

By way of further example, the geometry data 172 can be acquired usingnearly any imaging modality based on which a correspondingrepresentation of the geometrical surface can be constructed, such asdescribed herein. Such imaging may be performed concurrently withrecording the electrical activity that is utilized to generate thepatient measurement data 170 or the imaging can be performed separately(e.g., before or after the measurement data has been acquired).

Following (or concurrently with) determining electrical potential data(e.g., electrogram data computed from non-invasively acquiredmeasurements) across the geometric surface of the heart 152, aconduction pattern estimator 182 can process one or more intervals ofthe electrogram data to determine activation time across the surface.The conduction pattern estimator 182 constitutes instructions, which canbe implemented according to any of the approaches disclosed herein (see,e.g., FIGS. 1-6 and corresponding description), and thus can provideactivation times for each of the plurality of signals represented by theelectrogram data. The activation times can be aggregated with geometrydata to provide output data 174 to a display 192 for visualizing agraphical activation map (see, e.g., FIG. 6) 194 depicting a wave frontand propagation thereof across the heart surface based on the identifiedconduction patterns for such surface over one or more time intervals.

The mapping system 162 can also include an automated arrhythmia driveranalyzer method 182 to identify one or more drivers of cardiacarrhythmia, such as disclosed herein (e.g., corresponding toarrhythmogenic activity calculator 34). The arrhythmia driver analyzer182 can also be programmed to compute other characteristics associatedwith each identified arrhythmia driver, such as including driversustainability, trajectories of the rotational activity, wave frontlines, rotation count for of the rotational activity, rotation directionfor of the rotational activity, angular velocity for of the rotationalactivity, connectivity between rotating cores, cycle length and relatedstatistics associated therewith.

The mapping system 162 is programmed to combine the measurement data 170corresponding to electrical activity of the heart 152 with geometry data172 (e.g., corresponding to geometry data 57) by applying appropriateprocessing and computations to provide corresponding output data 174.The output data 174 can include data provided to the display 192 forvisualization of one or more graphical maps 194 and other relatedinformation to characterize one or more arrhythmia drivers, which can belocalized or global drivers across the cardiac envelope (e.g., on asurface of the heart 152).

The output generator (e.g., output engine 36) 186 can be programmed togenerate graphic maps based on the computed output data, such as notedabove. Parameters associated with the displayed graphicalrepresentation, corresponding to an output visualization of the computedmap, such as including selecting a time interval, a type of informationthat is to be presented in the visualization and the like can beselected in response to a user input via a graphical user interface(GUI) 190. For example, a user can employ the GUI 190 to selectivelyprogram one or more parameters (e.g., temporal and spatial thresholds,filter parameters and the like) utilized by the arrhythmia driveranalyzer method 182 and/or to select one or more sample time intervalsto set a time duration for the electrical data 170 that is utilized bythe mapping system 162. The mapping system 162 thus can generatecorresponding output data 174 that can in turn be rendered by the outputengine 186 as a corresponding graphical output in a display 192, such asincluding an electrocardiographic map 194. For example, the mapgenerator can generate maps and other output visualizations, such asincluding but not limited to the maps and other output visualizationsdisclosed herein.

Additionally, in some examples, the output data 174 can be utilized bythe therapy system 158. The control that is implemented can be fullyautomated control, semi-automated control (partially automated andresponsive to a user input) or manual control based on the output data174. In some examples, the control 160 of the therapy system can utilizethe output data 174 to control one or more therapy parameters. As anexample, the control 160 can control delivery of ablation therapy to asite of the heart (e.g., epicardial or endocardial wall) based onactivation timing or activation wave fronts determined by the conductionpattern estimator 182 and/or based on one or more arrhythmia driversidentified by the arrhythmia driver analyzer method 182. In otherexamples, an individual can view the map 194 generated in the display tomanually control the therapy system. Other types of therapy and devicescan also be controlled based on the output data 174 and correspondinggraphical map 194.

In view of the foregoing, it is understood that certain systems methodsdisclosed herein utilize the spatial continuity of a true activation todifferentiate the noise. As mentioned above, the use of filters toremove noise may also distort signal and activation detection. Thus,instead of using filter, systems and methods disclosed herein canidentify and remove noise-related detections based on its lack ofspatial footprint (i.e., no continuous activation from or towards itsspatial neighbors). Since this approach does not rely on filters, itavoids the creation of artifacts due to filters, and largely maintainsthe correct timing and morphology of the downward slopes, where theactivation happens and is detected.

Since this approach does not require the calculation of phase within acycle before the detection of activation, a shorter time interval fordata can now be processed, thereby reducing computational requirements.As a result, the visualization of such data is more focused on the wavefront instead of the entire cycle, which focuses the understanding ofconduction. In summary, the systems and methods herein (1) avoid signaldistortion due to filtering, (2) use a new and more robust way to pickthe activation time, (3) do not require phase calculation and is thuscapable of analyzing data with shorter duration, and (4) enable a newand easy-to-understand visualization mode for the activation wave front.

In view of the foregoing structural and functional description, thoseskilled in the art will appreciate that portions of the invention may beembodied as a method, data processing system, or computer programproduct. Accordingly, these portions of the present invention may takethe form of an entirely hardware embodiment, an entirely softwareembodiment, or an embodiment combining software and hardware.Furthermore, portions of the invention may be a computer program producton a computer-usable storage medium having computer readable programcode on the medium. Any suitable computer-readable medium may beutilized including, but not limited to, static and dynamic storagedevices, hard disks, optical storage devices, and magnetic storagedevices.

Certain embodiments of the invention have also been described hereinwith reference to block illustrations of methods, systems, and computerprogram products. It will be understood that blocks of theillustrations, and combinations of blocks in the illustrations, can beimplemented by computer-executable instructions. Thesecomputer-executable instructions may be provided to one or moreprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus (or a combination ofdevices and circuits) to produce a machine, such that the instructions,which execute via the processor, implement the functions specified inthe block or blocks.

These computer-executable instructions may also be stored incomputer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory result in an article of manufacture including instructions whichimplement the function specified in the flowchart block or blocks. Thecomputer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart block or blocks.

What have been described above are examples. It is, of course, notpossible to describe every conceivable combination of components ormethods, but one of ordinary skill in the art will recognize that manyfurther combinations and permutations are possible. Accordingly, theinvention is intended to embrace all such alterations, modifications,and variations that fall within the scope of this application, includingthe appended claims. Where the disclosure or claims recite “a,” “an,” “afirst,” or “another” element, or the equivalent thereof, it should beinterpreted to include one or more than one such element, neitherrequiring nor excluding two or more such elements. As used herein, theterm “includes” means includes but not limited to, the term “including”means including but not limited to. The term “based on” means based atleast in part on.

What is claimed is:
 1. A method, comprising: analyzing, by one or moreprocessors, a morphology and an amplitude of each of a plurality ofelectrophysiological signals captured by a plurality of sensorsdistributed across a surface of a patient's body to identify candidatesegments of each signal satisfying predetermined conduction patterncriteria; determining, by the one or more processors, a conductiontiming parameter for each candidate segment in each of theelectrophysiological signals; and causing, by the one or moreprocessors, a graphical map to be outputted on a display that includes avisualization of or derived based on the conduction timing parametersdetermined for the plurality of electrophysiological signals.
 2. Themethod of claim 1, wherein analyzing the morphology and the amplitudefurther comprises determining a set of potential segments in each of theelectrophysiological signals satisfying downward slope criteria.
 3. Themethod of claim 2, wherein determining the set of potential segmentsfurther comprises: selecting at least a portion of the candidatesegments from the set of potential segments based on the amplitude andduration thereof satisfying amplitude and duration criteria; anddesignating a portion from the set of potential segments for furtherevaluation.
 4. The method of claim 3, wherein the further evaluationcomprises: selecting, as one of the candidate segments, each segment inthe set of potential segments that is spatially and temporallyconsistent with neighboring candidates that have been selected andaggregating the candidate segments for each of the plurality ofelectrophysiological signals; and removing each respective segment fromfurther consideration in determining the conduction timing parameterthat is not spatially and/or temporally consistent with neighboringcandidates that have been selected.
 5. The method of claim 1, furthercomprising: acquiring electrical signals by a non-invasive arrangementof the plurality of sensors distributed on an outer body surface of thepatient; and computing reconstructed electrical signals on a cardiacenvelope with respect to an anatomical surface of the patient's heartbased on the acquired electrical signals and geometry data describingspatial locations of the plurality of sensors with respect to patientgeometry that includes the anatomical surface of the patient's heart. 6.The method of claim 1, wherein the method further comprises: computingan indication of arrhythmogenic activity based on the conduction timingparameter; generating the graphical map to visualize the indication ofarrhythmogenic activity with respect to the heart; and outputting thegraphical map to a display device.
 7. The method of claim 6, wherein theindication of arrhythmogenic activity comprises a number of focalpoints, a number of rotational activities and/or a trajectory of atleast one rotational activity, the indication of arrhythmogenic activitybeing displayed in the graphical map spatially with respect to theheart.
 8. The method of claim 6, further comprising storing data todocument user review of each indication of arrhythmogenic activitydisplayed in the graphical map in response to a corresponding user inputinteracting with the displayed indication of arrhythmogenic activity. 9.The method of claim 6, further comprising: removing a given indicationof arrhythmogenic activity displayed in the graphical map in response toa user input instruction to reject the given indication ofarrhythmogenic activity; and storing, in memory, data documenting theuser input instruction.
 10. The method of claim 1, wherein theconduction timing parameter is an activation time computed for each of aplurality of points on the surface over at least one time interval. 11.The method of claim 10, the method further comprising: selecting one ofa plurality of different activation time calculating functions based onat least one of noise, amplitude and morphology of the signals, theselected one of the activation time calculating functions performing theanalyzing to identify the candidate segments; and using the selectedactivation time calculating function to compute the conduction timingparameter as an activation time for the electrophysiological signals.12. A system comprising: memory to store machine readable instructionsand data, the data comprising electrical data representingelectrophysiological signals distributed across a body surface; at leastone processor to access the memory and execute the instructions, theinstructions comprising: a conduction pattern estimator that analyzes atleast a morphology that includes a downward slope of each of a pluralityof electrophysiological signals across a surface of a patient's body, toidentify candidate segments of each of the plurality ofelectrophysiological signals that satisfy predetermined conductionpattern criteria; a conduction pattern parameter identifier thatdetermines a conduction timing parameter for each of the identifiedcandidate segments in the electrophysiological signals; and an outputengine that provides output data to drive a display with a graphical mapthat includes a visualization of or derived based on the conductiontiming parameters determined for the electrophysiological signals. 13.The system of claim 12, wherein the conduction pattern estimator isfurther programmed to: determine a set of potential segments in each ofthe electrophysiological signals satisfying downward slope criteria;select at least a portion of the candidate segments from the set ofpotential segments based on an amplitude and duration thereof satisfyingamplitude and duration criteria; and designate another portion from theset of potential segments as questionable candidate segments for furtherevaluation.
 14. The system of claim 13, wherein the conduction patternestimator is further programmed to: select, as one of the candidatesegments, each segment in the set of potential segments that isspatially and temporally consistent with neighboring candidates thathave been selected and aggregating the candidate segments for each ofthe plurality of electrophysiological signals; and removing eachrespective segment from further consideration in determining theconduction timing parameter that is not spatially and/or temporallyconsistent with neighboring candidates that have been selected.
 15. Thesystem of claim 12, wherein the conduction timing parameter is anactivation time parameter, the further comprises locating an activationtime on the downward slope of each of the candidate segments.
 16. Thesystem of claim 15, further comprising a dynamic activation timeestimator that selects one of a plurality of different activation timecalculating functions based on at least one of a noise, an amplitude andthe morphology of the electrophysiological signals, the selected one ofthe activation time calculating functions analyzing the signal segmentsto identify the candidate segments; and the conduction pattern estimatorincluding a signal segment analyzer that employs the selected activationtime calculating function to determine the activation time for each ofthe electrophysiological signals.
 17. The system of claim 12, furthercomprising an arrhythmogenic activity calculator that computes anindication of arrhythmogenic activity based on the conduction timingparameter determined for the electrophysiological signals, wherein theoutput engine generates the graphical map to visualize the indication ofarrhythmogenic activity with respect to the heart.
 18. The system ofclaim 17, wherein the indication of arrhythmogenic activity comprises anumber of focal points, a number of rotational activities and/or atrajectory of at least one rotational activity, the indication ofarrhythmogenic activity being displayed in the graphical map spatiallywith respect to the heart.
 19. The system of claim 17, furthercomprising a user interface that stores user data in the memory todocument user review of each indication of arrhythmogenic activitydisplayed in the graphical map in response to a corresponding user inputinteracting with the displayed indication of arrhythmogenic activity,wherein the user interface modifies the stored user data to remove agiven indication of arrhythmogenic activity displayed in the graphicalmap in response to a user input instruction to reject the givenindication of arrhythmogenic activity.
 20. The system of claim 12,further comprising a signal segment detector that determines slope andpeaks for each of the plurality of electrophysiological signals, thesignal segment detector identifying downward sloping signal segmentsbased on the determined slope and peaks.
 21. The system of claim 12,further comprising: a non-invasive arrangement of sensors distributed onan outer body surface of the patient to acquire electrical signals froma plurality of locations on the outer body surface; and computingreconstructed electrical signals on a cardiac envelope with respect toan anatomical surface of the heart based on the acquired electricalsignals and geometry data describing spatial locations of the sensorswith respect to the patient geometry that includes the anatomicalsurface of the heart, the reconstructed electrical signals being storedin the memory as the plurality of electrophysiological signals.